1. Field of the Invention
The present invention is related to: whipstocks and associated apparatus for use in wellbores; whipstocks insertable through one tubular into another, e.g., but not limited to, through a smaller diameter tubing into a larger diameter casing; whipstock retrieval; anchoring apparatus for use in tubulars; and methods of use of such tools and apparatuses.
2. Description of Related Art
A variety of whipstocks and related milling systems are available in the prior art; e.g., but not limited to, the devices disclosed in U.S. Pat. Nos. 5,595,247; 5,772,972; 5,455,222; 5,452,759; 5,222,554; 5,211,715; 5,195,591; 5,109,924; 4,491,178; and 4,266,621.
Whipstocks and whipstock systems are tools inserted in a wellbore for deflecting a drill bit, mill, mill-drill, or other tool in a direction that is angularly offset with respect to the orientation wellbore. The deflected tool establishes a new or additional drilling path. In many instances, a whipstock set in a casing string on an anchor provides an angled whipstock surface or whipstock face at a desired depth in a wellbore to conduct side track or lateral directional drilling operations through a casing string. The face of the whipstock is oriented to position a casing window at a desired radial azimuth relative to the axis of the casing to provide a new drilling course.
Often a window is formed in a casing string that includes a smaller diameter tubing string that terminates at a position above a desired position of the casing window. Since the removal of the tubing string requires considerable rig time and expense, "through-tubing" whipstock systems have been developed for first passing through the tubing string then setting in a casing string at the desired depth for milling or cutting the window in the casing string. Once the window has been properly cut in the casing string, a side track or lateral drilling operation proceeds in a desired azimuthal direction relative to the casing string. Often a drill motor, and a bit rotatable by the drill motor, are suspended from a coiled tubing workstring for engaging a set whipstock in a casing string. Fluid is pumped through the coiled tubing workstring to drive the drill motor, so that the rotating bit engages the whipstock face and begins cutting a window in the casing string with an operation involving a single run-in trip of coiled tubing workstring.
There is a need for an effective whipstock and associated apparatus which is insertable through a smaller diameter tubular, such as tubing, and then disposable in a larger diameter tubular, such as casing, below the smaller diameter tubular. There is a need for such devices which effectively anchor and correctly orient themselves in the larger diameter tubular, and which are, in certain aspects, easily retrieved.